Question

php中mysql查询语句，变量的值无法用于mysql表达式中

<?php
$con=mysql_connect("XXXXX", "XXXXXXX", "XXXXXX");

mysql_select_db("XXXXXX");

mysql_close($con);

$a="accountname";

$result1=mysql_query("SELECT * FROM userinformation WHERE Accountname=$a");

$row1=mysql_fetch_row($result1);

mysql_close($con);

?>
脚本运行后报错：
Warning: mysql_fetch_row(): supplied argument is not a valid MySQL result resource in /home/content/51/11444851/html/script/likepoints_increase.php on line 27

但是将语句
$result1=mysql_query("SELECT * FROM userinformation WHERE Accountname=$a");
更改为
$result1=mysql_query("SELECT * FROM userinformation WHERE Accountname=‘accountname'");
后，脚本运行却正常

数据库无损坏，字段类型

Accountname varchar(50)
utf8_bin

Answer 1

少了单引号:
$result1=mysql_query("SELECT * FROM userinformation WHERE Accountname='".$a."'");

Answer 2

<?php
$con=mysql_connect("XXXXX", "XXXXXXX", "XXXXXX");

mysql_select_db("XXXXXX");

mysql_close($con);

$a="accountname";
$sql="SELECT * FROM userinformation WHERE Accountname='".$a."'";
$result1=mysql_query($sql);

$row1=mysql_fetch_row($result1);

mysql_close($con);

?>